FATZ, a filamin-, actinin-, and telethonin-binding protein of the Z-disc of skeletal muscle.

We report the identification and characterization of a novel 32-kDa protein expressed in skeletal muscle and located in the Z-disc of the sarcomere. We found that this protein binds to three other Z-disc proteins; therefore, we have named it FATZ, gamma-filamin/ABP-L, alpha-actinin and telethonin binding protein of the Z-disc. From yeast two-hybrid experiments we are able to show that the SR3-SR4 domains of alpha-actinin 2 are required to bind the COOH-terminal region of the FATZ as does gamma-filamin/ABP-L. Furthermore, by using a glutathione S-transferase overlay assay we find that FATZ also binds telethonin. The level of FATZ protein in muscle cells increases during differentiation, being clearly detectable before the onset of myosin. Although FATZ has no known interaction domains, it would appear to be involved in a complex network of interactions with other Z-band components. On the basis of the information known about its binding partners, we could envisage a central role for FATZ in the myofibrillogenesis. After screening our muscle expressed sequence tag data base and the public expressed sequence tag data bases, we were able to assemble two other muscle transcripts that show a high level of identity with FATZ in two different domains. Therefore, FATZ may be the first member of a small family of novel muscle proteins.

Ancestral hemoglobin switching in lampreys.

A very simple hemoglobin switching was discovered in the lamprey Lampetra zanandreai. A single larval globin cDNA and two adult globin cDNAs were fully sequenced and their differential expression during lamprey development was investigated. The evolutionary positions of these new globin sequences are also discussed.

Comparative analysis of the region of the mitochondrial genome containing the ATPase subunit 9 gene in the two related yeast species Saccharomyces douglasii and Saccharomyces cerevisiae.

We have determined the nucleotide sequence of a region of the mitochondrial genome of the yeast Saccharomyces douglasii which contains the ATPase subunit 9 gene and part of the intergenic sequences that surround it. The gene is 228 nucleotides long and encodes a polypeptide of 76 aa. A comparison of the coding sequence with that of S. cerevisiae reveals the presence of three silent transitions. A high level of similarity is also found between regions involved in the initiation of transcription and mRNA processing. More interestingly, a region of similarity situated outside the known regulatory regions has been identified. As the intergenic regions are generally highly divergent, the remarkable conservation of these non-coding sequences suggests that their structure may be relevant to the expression of this region of the mitochondrial DNA.

Different globin messenger RNAs are present before and after the metamorphosis in Lampetra zanandreai.

Lampreys are very primitive vertebrates belonging to the Agnata group. Although higher vertebrates have polymeric hemoglobin molecules which are encoded by several differentially expressed genes, lampreys have monomeric hemoglobins. However, it is unclear whether one or more globin genes are present. In this paper we show that four different species of globin can be separated by electrophoresis in acetic acid-urea-Triton gels. Two of the four species are present only before metamorphosis, while the other two are present only during adult life. In order to discover whether these differences are due to post-translational modifications of a unique amino acid sequence, we extracted globin mRNAs from both larval and adult stages and translated them in vitro. We found that both larval and adult globin mRNAs produce single globin bands; however, larval and adult bands are different from each other. Our data are consistent with the idea that two different globin genes are present in lampreys and that they are differentially expressed during development.